From WO 2006/100044, the entire contents of which is incorporated herein by reference, a method for shredding and cleaning of waste plastics, mixed plastics in particular, has become known, in which a compacted mass or an agglomerate, respectively, is made from foil scraps or other foil remnants and chopped plastic parts. The agglomerate reduces the volume of the waste plastics drastically, and thus, it can be transported easily. It is used in this condition for energy production to a large extent. In the known method, it is started from the finding that such a compacted mass or agglomerate, respectively, can be easily ground, and the ground product is very suitable for further treatment and upgrading conversion. The grinding takes place in a disc- or drum refiner in the presence of water. The proportion of flakes and other particles is at least 10% of the total volume. Substances adhering on the flakes are rubbed down to a large extent and are present as separate substances. A fine grain fraction is removed from the ground product leaving the refiner. The remaining ground product is washed or mechanically dewatered and dried, respectively. By further treatment, such a ground product can be used as a raw material and/or filler for board materials, as filler for quite different applications, and at corresponding degree of purification even with pure plastics or plastics from sorting processes for the production of plastics components. A further field of application is the production of so-called WPC-parts (Wood Plastics Composites). In the production of such parts, a mixture of wood- and plastic particles is produced either by dry mixing and direct processing, or by compounding with the aid of an extruder, an agglomerator, a heating mixer or a heating-cooling mixer, and processed into moulded articles.
Of course, waste plastics contains a not insignificant fraction of contaminants and adhering substances, of wood pulp in particular, which is of no use for many fields of application. This wood pulp originates from adhesive labels, from composite packages or from incomplete removal of free paper. In plastics from used paper collections, great amounts of wood pulp adhere frequently on the plastics. In the compacting, the wood pulp is melt in or encapsulated, respectively, and arrives in the grinding process due to this. Even after the grinding, wood pulp is still incorporated into individual grains or particles of the ground product or still adheres on the grains or particles of the ground product. When plastics is processed together with wood pulp in an extruder or in an injection moulding machine, the humidity of the wood pulp leads to the generation of water vapour, which makes processing harder or even impossible. In addition, wood pulp in the ground condition has the disadvantage that it attracts moisture by its hygroscopic effects, which persists longer than in the plastic material in a drying process, as the case may be.
EP 515946, the entire contents of which is incorporated herein by reference, discloses a method for separating textile fibres from waste plastics, in which the shredded product is charged into a disc refiner together with water, without previously producing a compacted mass or agglomerate, respectively, from the flakes and the particles.
JP 2003 305 724, the entire contents of which is incorporated herein by reference, discloses a method for separating paint layers from waste plastics, in which the shredded product is charged into a disc refiner together with a solvent, without previously producing a compacted mass or agglomerate, respectively, from flakes and particles.
Compacting or agglomerating, respectively, is a process that requires high apparatus energy consumption and thus is very cost-expensive. Furthermore, agglomerate is not always at hand.
Consequently, the present invention is based on the objective to indicate a method for the removal of wood pulp and other adhering substances from waste plastics in the recycling of waste plastics, which reduces the expense with respect to energy and apparatus.